<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>5.1</title>
</head>
<body>
    <form action="experiment_5_1" method="post">
    username：<input type="text" name="un"/><br/>
    <input type="submit" value="登录"/>
    <input type="reset" value="重置"/>
</form>
</body>
</html>